round of decimal value in c++ code example

Example 1: round double to n decimal places c++

float roundoff(float value, unsigned char prec)
{
  float pow_10 = pow(10.0f, (float)prec);
  return round(value * pow_10) / pow_10;
}

auto rounded = roundoff(100.123456, 3);
// rounded = 100.123;

Example 2: round double to n decimal places c++

value = round( value * 100.0 ) / 100.0; // 2 decimal places
value = round( value * 1000.0 ) / 1000.0; // 3 decimal places

Example 3: round double to 2 decimal places c++

double d = 0.12345;
std::cout.precision(2); // for accuracy to 2 decimal places 
std::cout << d << std::endl; // 0.12